Thin provisioned space allocation

ABSTRACT

A storage monitoring system may reside between a file system and a storage system in a thin provisioned storage system. The storage monitoring system may create space holder files within a volume, where the space holder files contain an address space not backed up with physical storage. As requests for storage space are received from a file system, the storage monitoring system may allocate physical space to the volume by provisioning portions of the physical storage device to the volume and by removing one of the space holder files. The storage monitoring system may present alerts when physical storage space is low, as well as return an amount of physical space available to a volume size request.

BACKGROUND

Storage systems that use thin provisioning may present a very largelogical capacity to a file system, when in fact the storage system maynot be fully backed by physical storage. In such systems, the filesystem may operate as if the large logical capacity exists, but when thephysical storage nears capacity, data may be lost if the file systemcontinues to write data to the storage.

In one use scenario, thin provisioning may be used in many systems wheremultiple volumes may be stored on a single set of physical storage. Whenthe physical storage may be configured, an administrator may not knowhow much physical space each volume may use over time. Rather thanpartitioning the physical drive, multiple volumes may be thinprovisioned. This may allow any of the logical volumes to use thephysical storage resource until the physical storage is full.

SUMMARY

A storage monitoring system may reside between a file system and astorage system in a thin provisioned storage system. The storagemonitoring system may create space holder files within a volume, wherethe space holder files contain an address space not backed up withphysical storage. As requests for storage space are received from a filesystem, the storage monitoring system may allocate physical space to thevolume by provisioning portions of the physical storage device to thevolume and by removing one of the space holder files. The storagemonitoring system may present alerts when physical storage space is low,as well as return an amount of physical space available to a volume sizerequest.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a diagram illustration of an embodiment showing a system witha provisioning engine.

FIG. 2 is a timeline illustration of an embodiment showing a method forprocessing file system commands.

FIG. 3 is a timeline illustration of an embodiment showing an additionalmethod for processing file system commands.

FIG. 4 is a flowchart illustration of an embodiment showing a method foradjusting allocated space downward.

FIG. 5 is a flowchart illustration of an embodiment showing a method foradjusting allocated space upward.

DETAILED DESCRIPTION

A thin provisioned file system may use space holder files to occupyspace within volumes, then release the space holder files to provisionthe volumes with physical storage space. A provisioning engine maymonitor the allocated space and physical space and may be able to issuea low space warning prior to running out of physical storage space.

The system may operate by filling all of the logical volumes with spaceholder files. The space holder files may have addresses that are outsideof the physical storage media and may appear as full volumes even whenthe volumes contain little or no data. As applications request morephysical storage, the system may remove a space holder file and allocatephysical space to the volume in the amount that the space holder fileconsumed.

A standard file system may be used by the system to manage files withinthe storage system and to respond to various file related commands.However, a communications layer may intercept the commands fromapplications and may ensure that enough physical space is available torespond to a file related command. The communications layer may alsointercept available space requests and may process those requestsseparately from the file system.

Throughout this specification and claims, references may be made tological volumes or storage and physical storage. Physical storage mayrefer to actual, physical storage capacity of a nonvolatile storagesystem. An example of physical storage may be a hard disk drive. Alogical volume may be an addressable space in which a file system mayoperate by adding, editing, and deleting files, but the logical volumemay not directly correspond with physical storage. In many embodiments,the logical volume may be the object with which a file system mayinteract, and a separate space management system may provide physicalstorage to store items within the logical volume.

Throughout this specification, like reference numbers signify the sameelements throughout the description of the figures.

When elements are referred to as being “connected” or “coupled,” theelements can be directly connected or coupled together or one or moreintervening elements may also be present. In contrast, when elements arereferred to as being “directly connected” or “directly coupled,” thereare no intervening elements present.

The subject matter may be embodied as devices, systems, methods, and/orcomputer program products. Accordingly, some or all of the subjectmatter may be embodied in hardware and/or in software (includingfirmware, resident software, micro-code, state machines, gate arrays,etc.) Furthermore, the subject matter may take the form of a computerprogram product on a computer-usable or computer-readable storage mediumhaving computer-usable or computer-readable program code embodied in themedium for use by or in connection with an instruction execution system.In the context of this document, a computer-usable or computer-readablemedium may be any medium that can contain, store, communicate,propagate, or transport the program for use by or in connection with theinstruction execution system, apparatus, or device.

The computer-usable or computer-readable medium may be for example, butnot limited to, an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, device, or propagationmedium. By way of example, and not limitation, computer-readable mediamay comprise computer storage media and communication media.

Computer storage media includes volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information such as computer-readable instructions, data structures,program modules, or other data. Computer storage media includes, but isnot limited to, RAM, ROM, EEPROM, flash memory or other memorytechnology, CD-ROM, digital versatile disks (DVD) or other opticalstorage, magnetic cassettes, magnetic tape, magnetic disk storage orother magnetic storage devices, or any other medium which can be used tostore the desired information and may be accessed by an instructionexecution system. Note that the computer-usable or computer-readablemedium can be paper or other suitable medium upon which the program isprinted, as the program can be electronically captured via, forinstance, optical scanning of the paper or other suitable medium, thencompiled, interpreted, of otherwise processed in a suitable manner, ifnecessary, and then stored in a computer memory.

Communication media typically embodies computer-readable instructions,data structures, program modules or other data in a modulated datasignal such as a carrier wave or other transport mechanism and includesany information delivery media. The term “modulated data signal” can bedefined as a signal that has one or more of its characteristics set orchanged in such a manner as to encode information in the signal. By wayof example, and not limitation, communication media includes wired mediasuch as a wired network or direct-wired connection, and wireless mediasuch as acoustic, RF, infrared and other wireless media. Combinations ofany of the above-mentioned should also be included within the scope ofcomputer-readable media.

When the subject matter is embodied in the general context ofcomputer-executable instructions, the embodiment may comprise programmodules, executed by one or more systems, computers, or other devices.Generally, program modules include routines, programs, objects,components, data structures, and the like, that perform particular tasksor implement particular abstract data types. Typically, thefunctionality of the program modules may be combined or distributed asdesired in various embodiments.

FIG. 1 is a diagram of an embodiment 100, showing a system that mayinclude a provisioning engine for managing a thinly provisioned storagesystem. Embodiment 100 is a simplified example of a hardware andsoftware environment in which a provisioning engine may operate.

The diagram of FIG. 1 illustrates functional components of a system. Insome cases, the component may be a hardware component, a softwarecomponent, or a combination of hardware and software. Some of thecomponents may be application level software, while other components maybe operating system level components. In some cases, the connection ofone component to another may be a close connection where two or morecomponents are operating on a single hardware platform. In other cases,the connections may be made over network connections spanning longdistances. Each embodiment may use different hardware, software, andinterconnection architectures to achieve the described functions.

Embodiment 100 is an example of a system in which a thinly provisionedstorage system may operate. The thinly provisioned storage system mayhave one or more logical volumes in which a file system may store andmanage files, but where the space assigned to the volumes is more thanthe physical space available to store the volumes.

Thinly provisioned storage systems may be useful when multiple volumesmay be stored on a single physical storage system. In an example, fourvolumes may be created on a physical storage system. At the time thevolumes are created, it may not be known how much space each volume mayeventually consume, so each volume may be created with the same storagespace as the physical storage system. In such a situation, any volumemay grow to consume the entire physical storage system. However, thephysical storage system may be at full capacity while each volume ismerely one quarter full.

Thinly provisioned storage systems may also be useful when a volume maybe expected to grow over time, but a user may not wish to purchase allof the physical storage devices at startup. As the physical storagebecomes used up, the user may be able to add more physical storagedevices without changing the volume configuration.

The storage system may use a conventional file system to process manyfile related commands. Typical file systems are mechanisms for storingand organizing computer files and their data. A generic file system mayorganize the files into a database for the storage, organization,manipulation, and retrieval by a computer operating system. There aremany different forms and implementation of file systems, each of whichmay have different advantages, disadvantages, and may be suitable tocertain hardware or software configurations.

Embodiment 100 illustrates a mechanism whereby a file system that maynot have support for thin provisioning may be converted to a thinprovisioning system. Embodiment 100 may also illustrate an architecturefor a thin provisioned storage system where a thin provisioned featuremay be added or removed from the file system.

The thin provisioned storage system may create multiple space holderfiles to fill up each volume and consume address space within thevolume. The space holder files may not be backed up or provisioned withphysical storage, but may be deleted to free up space within a volume.The freed space within the volume may be provisioned with physicalstorage space and used by the file system.

Because the volumes may have much of the address space occupied by spaceholder files, the volume may appear to the file system as having only asmall amount of available space. The file system may use the availablespace when creating new files or adding to existing files. The availablespace may be used up over time, and when the amount of available spacebecomes less than a lower threshold, one or more space holder files maybe removed and the space allocated to the space holder files may becomefree to be addressed by the file system.

Some file systems may consume physical storage space in a randomized orhaphazard fashion, and may spread files across all the available addressspace. The space holder files may limit the amount of available spacewithin the physical storage for each volume, and may control or minimizesome file system's propensity to disperse files over a large area. Someembodiments may have the ability to condense or consolidate volumes,move volumes, or perform other such operations. Having files in acontiguous space may speed up or enable such operations.

The architecture of embodiment 100 has a communications layer that mayintercept communications between an application and a file system. Thecommunications layer may redirect some file system commands and performsome processing prior to allowing the file system to process thecommands.

For example, when an application sends a file system command that mayrequest additional physical storage space, the communications layer mayintercept the command and determine whether or not additional physicalstorage space may be used by the command. If so, space holder files maybe removed to free up space to respond to the command.

In another example, a request for the available free space on the volumemay be intercepted and processed without calling the file system. Thestorage system may calculate the available free space by determining theactual unused physical storage space. Such a request may be handled by aprovisioning engine without sending the request to the file system.

Embodiment 100 illustrates a device 102 that may have a system formanaging a thin provisioned storage system. The device 102 may haveseveral volumes with addressable space, the sum of which may exceed thephysical storage space available.

The device 102 is illustrated having hardware components 104 andsoftware components 106. The controller device 102 as illustratedrepresents a conventional computing device, although other embodimentsmay have different configurations, architectures, or components.

The controller device 102 may be a server computer, desktop computer, orcomparable device. In some embodiments, the controller device 102 may bea laptop computer, netbook computer, tablet or slate computer, wirelesshandset, cellular telephone, or any other type of computing device.

The hardware components 104 may include a processor 108, random accessmemory 110, and nonvolatile storage 112. The hardware components 104 mayalso include a user interface 114 and network interface 116. Theprocessor 108 may be made up of several processors or processor cores insome embodiments. The random access memory 110 may be memory that may bereadily accessible to and addressable by the processor 108. Thenonvolatile storage 112 may be storage that persists after the device102 is shut down. The nonvolatile storage 112 may be any type of storagedevice, including hard disk, solid state memory devices, magnetic tape,optical storage, or other type of storage. The nonvolatile storage 112may be read only or read/write capable.

The nonvolatile storage 112 may be a collection of storage devices. Insome embodiments, a set of storage devices, such as disk drives, may bearranged together to provide a large amount of nonvolatile storage. Insome embodiments, several devices may be aggregated using RedundantArray of Independent Disks (RAID) technologies. Many RAID systems mayuse storage devices of the same capacity to create a large storagesystem.

Some embodiments may be capable of aggregating storage devices that havedifferent storage capacities and may use different hardwaretechnologies. For example, such embodiments may aggregate a conventionaldisk drive accessed on a IDE interface with another disk drive connectedusing a Universal Serial Bus (USB) connection, along with a solid statestorage device connected using a Small Computer System Interconnect(SCSI) interface.

Some embodiments may configure one or more volumes to be duplicated ontwo or more different storage devices. Such duplication may provideredundancy in the event of a failure of a single storage device. When avolume may be duplicated on two storage devices, such a volume mayconsume approximately twice the physical storage as a volume for whichno duplication is performed.

The user interface 114 may be any type of hardware capable of displayingoutput and receiving input from a user. In many cases, the outputdisplay may be a graphical display monitor, although output devices mayinclude lights and other visual output, audio output, kinetic actuatoroutput, as well as other output devices. Conventional input devices mayinclude keyboards and pointing devices such as a mouse, stylus,trackball, or other pointing device. Other input devices may includevarious sensors, including biometric input devices, audio and videoinput devices, and other sensors.

The network interface 116 may be any type of connection to anothercomputer. In many embodiments, the network interface 116 may be a wiredEthernet connection. Other embodiments may include wired or wirelessconnections over various communication protocols.

The software components 106 may include an operating system 118 on whichvarious applications and services may operate. An operating system mayprovide an abstraction layer between executing routines and the hardwarecomponents 104, and may include various routines and functions thatcommunicate directly with various hardware components.

The operating system 118 may include several components for managingthin provisioned storage. A file system 120 may manage files in adatabase and may respond to various commands and requests. Surroundingthe file system 120 may be a communications layer 122 that may interceptand process communications between applications 128 and the file system120. A space management system 124 may operate in between the filesystem 120 and the physical storage 112. A provisioning engine 126 maymanage the various components to provide a thin provisioned storagesystem using the file system 120.

The file system 120 may provide file management functions, such ascreating, deleting, and editing files. Many file systems may also permitusers to organize files into directories or folders, and may permitoperations to be performed on groups of files. Many different filesystems are commercially available.

The thin provisioned storage system may use a conventional file systemto perform some functions, but may perform additional operations beforeor after having the file system perform certain functions. In somecases, the thin provisioned storage system may perform operationsseparately and independently from the file system.

The thin provisioned storage system may manage the allocated physicalspace for each volume independently from the file system. When requestsare received that may utilize more physical space than may be allocatedto a specific volume, the space management system 124 may allocatephysical space by manipulating various space holder files.

A request may be received by the communications layer 122, and therequest may be analyzed to determine whether or not enough free physicalspace may be available to successfully perform the request. In oneembodiment, a provisioning engine 126 or other component may analyze therequest to determine available free physical space.

In another embodiment, the request may be transmitted to the file system120. If a disk full error is returned, the communications layer 122 mayintercept the error and cause the space management system 124 toallocate additional space. After additional space is allocated, thecommunications layer 122 may re-issue the original request to the filesystem 120.

The space management system 124 may allocate and de-allocate physicalspace to volumes. The space management system 124 may create multiplespace holder files within the volumes, and may add or remove the spaceholder files to allocate and de-allocate physical space.

A space holder file may be created by a space management system in anaddress area that is not provisioned within the logical volume. When aspace holder file may be deleted, the address space may be allocated tothe physical storage system. When a space holder file may be created,the address space consumed by the space holder file may be released fromthe physical storage system if the space were already allocated.

The provisioning engine 126 may monitor the operations of thecommunications layer 122 and space management system 124 and mayfacilitate communication between the communication layer 122 and thespace management system 124. The provisioning engine 126 may causecertain operations to be performed, and may perform some of thoseoperations or may cause the communications layer 122, space managementsystem 124, or the file system 120 to perform some operations.

The storage system of device 102 may use several different types ofstorage devices. In a conventional computer system, a hard disk or solidstate storage device may be mounted internal to the computer. Somedevices may have various peripheral storage devices 130, which may be anexternal hard disk or solid state storage device connected using USB,SCSI, or other type of interface.

Some devices may have storage that may be available through a network132 and may be network storage devices 134. The network storage devicesmay be a Storage Area Network (SAN), a storage device connected througha local area network, a storage device connected through a wide areanetwork such as the Internet, a cloud storage system, or any other typeof storage device.

The various storage devices may be used independently or aggregatedtogether to provide physical storage for the thin provisioned volumes.The provisioning engine 126 and the other components may operate toprovide thin provisioned volumes across one or more storage devices.

FIG. 2 is a timeline illustration of an embodiment 200 showing a methodfor processing file system commands. The process of embodiment 200 is asimplified example of how an application 202 may interact with acommunication layer 204, file system 206, and space management system208 to deliver a thin provisioned storage system.

Other embodiments may use different sequencing, additional or fewersteps, and different nomenclature or terminology to accomplish similarfunctions. In some embodiments, various operations or set of operationsmay be performed in parallel with other operations, either in asynchronous or asynchronous manner. The steps selected here were chosento illustrate some principles of operations in a simplified form.

Embodiment 200 is a timeline illustration, where the operations of theapplication 202 are shown in the left hand column, the operations of thecommunication layer 204 are shown in the second column, the operationsof the file system 206 are shown in the third column, and the operationsof the space management system 208 are shown in the right hand column.

Embodiment 200 is an example of an embodiment where commands may beintercepted and analyzed prior to executing the commands with a filesystem. If the commands may consume more physical storage space than maybe currently allocated, additional physical storage space may beallocated.

An application 202 may transmit a file system command in block 210. Thefile system command of block 210 may be any type of operation which thefile system 206 may be capable of performing. The actual commands maydepend on the specific file system being used, but in general thecommands may include creating, editing, and deleting files. Many filesystems may have additional commands for performing directory or folderoperations, plus many additional file specific operations.

The communication layer 204 may receive the file system command in block212 and may perform some analysis of the command. If the command doesnot change the file size in block 214, the command may be transmitted tothe file system 206 in block 216, where the file system 206 may receivethe command in block 218, process the command in block 220, and return aresponse in block 222. The communication layer 204 may receive theresponse in block 224 and transmit the response in block 226 to theapplication 202. The application 202 may receive the response in block228.

In contrast to the operations of blocks 216-228, if the command maychange the file size in block 214, the command may be transmitted to thespace management system in block 230. The space management system 208may receive the command in block 232 and may analyze the spaceallocation in block 234. If the physical space may be adjusted inresponse to the command in block 236, the physical space adjustments maybe made in block 238. After processing, the command may be transmittedin block 240 to the file system 206.

The file system 206 may receive the command in block 242, process thecommand in block 244, and transmit a response in block 246. Thecommunication layer 204 may receive the response in block 248 andtransmit the response in block 250 to the application 202, which mayreceive the response in block 252.

The adjustments of block 238 may be to allocate additional physicalspace to a volume. An example of such an operation may be found inembodiment 500 presented later in this specification. In some cases, theadjustments made in block 238 may be to deallocate additional physicalspace to a volume. An example of such an operation may be found inembodiment 400 presented later in this specification.

Embodiment 200 illustrates an example embodiment where a file systemcommand may be analyzed prior to sending the command to the file system.In another embodiment, the communication layer may permit the command tobe transmitted to the file system, but may intercept the response of thefile system before the application receives the response. Thecommunications layer may determine that a disk full error may haveoccurred. If so, the communications layer may communicate with the spacemanagement system to cause additional physical space to be allocated.The initial file system command may be re-transmitted to the file systemand the process re-tried.

FIG. 3 is a timeline illustration of an embodiment 300 showing a methodfor processing a space request command. The process of embodiment 200 isa simplified example of how an application 202 may interact with acommunication layer 204, file system 206, and space management system208 to deliver a thin provisioned storage system.

Other embodiments may use different sequencing, additional or fewersteps, and different nomenclature or terminology to accomplish similarfunctions. In some embodiments, various operations or set of operationsmay be performed in parallel with other operations, either in asynchronous or asynchronous manner. The steps selected here were chosento illustrate some principles of operations in a simplified form.

Embodiment 200 is a timeline illustration, where the operations of theapplication 202 are shown in the left hand column, the operations of thecommunication layer 204 are shown in the second column, the operationsof the file system 206 are shown in the third column, and the operationsof the space management system 208 are shown in the right hand column.

In block 252, an application 202 may transmit a storage space request. Astorage space request may request the available storage for a particularvolume. In the case of a thin provisioned storage system, the logicalvolumes may have a large amount of addressable storage, but the physicalstorage may not be as large as the addressable storage.

In many cases, an application 202 may request the available storagespace so that the application may perform various checks prior toperforming an operation. For example, an application may ensure thatsufficient storage space may be available prior to instantiating adatabase or prior to creating a new data file.

From the standpoint of the file system, very little storage space mayappear to be available. This may be because the logical volumes may havemany space holder files which may fill the addressable space, leaving asmall amount of addressable space to create new files. Rather thantransmit the available storage space request to the file system whichmay return a number substantially lower than the actual physical spaceavailable, the available storage space request may be handled by thespace management system 208.

The application 202 may transmit a storage space request in block 252,which may be received in block 254 by the communication layer 204. Thecommunication layer 204 may analyze the communication and determine thatthe communication may be processed by the space management system 208.The communication layer 204 may transmit the request in block 256, whichmay be received by the space management system 208 in block 258.

The space management system 208 may determine the available physicalstorage capacity in block 260, and may return a response in block 262 tothe communications layer 204. The communications layer 204 may receivethe response in block 264, then transmit the response in block 266 tothe application 202, which may receive the response in block 268.

The available physical storage capacity determined in block 260 may notcorrespond with the available logical storage space, but may correspondwith the available physical storage space. The available physicalstorage space may be calculated by determining the largest file sizethat could be stored on the physical storage and returning that value.

The available physical storage space may include the empty allocatedphysical storage space plus the empty unallocated physical storagespace. In some embodiments, the available physical storage space mayinclude the empty allocated physical storage space for the currentvolume, plus the empty unallocated physical storage space that has notbeen allocated to other volumes.

In embodiments where certain volumes may be duplicated on two or morephysical storage devices, the available physical storage space may bereduced accordingly. For example, the space available in a duplicatedvolume may be the amount of space available on the smaller of twophysical storage devices assigned to the volume. Other embodiments mayhave different methods to calculate the available storage, depending onthe physical configuration of the storage devices and other factors.

FIG. 4 is a flowchart illustration of an embodiment 400 showing a methodfor adjusting allocated space in a volume downward. The process ofembodiment 400 may be used in several situations to fill up a volumewith space holder files.

Other embodiments may use different sequencing, additional or fewersteps, and different nomenclature or terminology to accomplish similarfunctions. In some embodiments, various operations or set of operationsmay be performed in parallel with other operations, either in asynchronous or asynchronous manner. The steps selected here were chosento illustrate some principles of operations in a simplified form.

Embodiment 400 is an example of how space holder files may be createdwithin a logical volume to consume much of the addressable storagespace. As storage space may be used, the space holder files may beremoved and physical storage space allocated to the volume. An exampleof such a process may be found in embodiment 500 presented later in thisspecification.

Embodiment 400 may be invoked in several different situations. A newvolume may be created in block 402 and a volume size may be assigned inblock 404. In another situation, a request may be made to increase thevolume size in block 406. In yet another situation, files may be deletedor shrunk in block 408. In any of these events, the amount of free spacewithin the volume may exceed an upper threshold and space holder filesmay be added.

The allocated free space within the volume may be determined in block410. If the amount of allocated free space is greater than an upperthreshold in block 412, a space holder file may be created in block 416and the physical space consumed by the space holder file may bedeallocated in block 418. The process may loop back to block 410repeatedly until the allocated free space is less than the upperthreshold in block 412 in which case the process may end in block 414.

FIG. 5 is a flowchart illustration of an embodiment 500 showing a methodfor adjusting the allocated space in a volume upward. The process ofembodiment 500 may be used in several situations where additional spacemay be requested by a volume.

Other embodiments may use different sequencing, additional or fewersteps, and different nomenclature or terminology to accomplish similarfunctions. In some embodiments, various operations or set of operationsmay be performed in parallel with other operations, either in asynchronous or asynchronous manner. The steps selected here were chosento illustrate some principles of operations in a simplified form.

Embodiment 500 is an example of how space holder files may be removedfrom a logical volume and physical storage may be allocated to thelogical volume. The process may be performed until no further spaceholder files may be available, which may indicate that the physicalstorage has been consumed and an alert may be issued.

Embodiment 500 may be invoked in several different situations. A volumesize may be shrunk in block 502 or files may be added or expanded inblock 504.

The allocated free space within the volume may be determined in block506. If the amount of allocated free space is less than a lowerthreshold in block 508 and space holder files are available within thevolume in block 510, a space holder file may be removed in block 516 andthe physical space consumed by the space holder file may be allocated inblock 518. The process may loop back to block 506 repeatedly until theallocated free space is larger than the lower threshold in block 508, inwhich case the process may end in block 510.

If the allocated free space is less than the lower threshold in block508 but no more space holder files are available in block 512, a lowphysical space alert may be issued in block 514. The low physical spacealert of block 514 may be transmitted to a user or administrator of acomputer system and may indicate that the physical storage may be fullyutilized. The user or administrator may add additional physical storagedevices or may remove files, compress the volumes, or otherwise use thephysical storage space more efficiently.

The foregoing description of the subject matter has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the subject matter to the precise form disclosed,and other modifications and variations may be possible in light of theabove teachings. The embodiment was chosen and described in order tobest explain the principles of the invention and its practicalapplication to thereby enable others skilled in the art to best utilizethe invention in various embodiments and various modifications as aresuited to the particular use contemplated. It is intended that theappended claims be construed to include other alternative embodimentsexcept insofar as limited by the prior art.

What is claimed is:
 1. A method performed on a computer processor, saidmethod comprising: creating a plurality of space holder files on athinly provisioned storage volume, said space holder files comprising anaddress space in said thinly provisioned storage volume for which nophysical storage has been assigned; operating a file system with saidthinly provisioned storage volume and a physical storage system;intercepting a file system command that requests file space; determiningif said file system command consumes more physical storage space thanwhat is currently provisioned and provisioning said thinly provisionedstorage volume with a portion of said physical storage system, saidportion being at least a size equal to one of said space holder files;and removing one of said space holder files from said file system suchthat said file system allocates storage space in response to said filesystem command.
 2. The method of claim 1 further comprising: determiningthat less than a lower threshold of space is available on said thinlyprovisioned storage volume and removing at least one of said spaceholder files.
 3. The method of claim 2 further comprising: removing aplurality of said space holder files until available space is higherthan said lower threshold.
 4. The method of claim 2 further comprising:determining that more than an upper threshold of space is available onsaid thinly provisioned storage volume and adding at least one of saidspace holder files to said file system.
 5. The method of claim 1 furthercomprising: receiving a volume size request for said thinly provisionedstorage volume and determining an amount of physical space available andreturning said amount of physical space available.
 6. The method ofclaim 5, said amount of physical space available comprising emptyallocated physical space and empty unallocated physical space.
 7. Astorage space management system comprising: a file system that managesfiles stored in said storage space management system; a connection to aphysical storage system; a set of volumes being thinly provisioned onsaid physical storage system; a communications layer that receivescommunications between an application and said file system; a spacemanagement system that creates a plurality of space holder files withinan address space of said set of volumes, said address space being withinsaid set of volumes for which no physical storage has been assigned; aprovisioning engine that: detects a file system command received on saidcommunications layer, said file system command being transmitted from anapplication; transmits said file system command to said file system andreceives a disk full response; detects said disk full response andprovisions at least one of said volumes by deleting one of said spaceholder files; and re-transmits said file system command to said filesystem where said file system responds with a response other than a diskfull error.
 8. The system of claim 7, said connection to a physicalstorage system comprising a network connection.
 9. The system of claim7, said file system command comprising a command that consumesadditional storage space.
 10. The system of claim 9, said file systemcommand comprising a write command, said write command being successfulafter said re-transmit.
 11. The system of claim 10, said disk fullresponse not being transmitted to said application.
 12. The system ofclaim 11, said disk full response being transmitted to said applicationonly when said physical storage is full.
 13. The system of claim 12,said file system command being one of a group composed of: create file;and edit file.
 14. The system of claim 7, said management engine thatfurther: receives a storage space query and returns a space valueequivalent to a maximum file size that is created on said physicalstorage system by said storage space management system.
 15. The systemof claim 14, at least one of said volumes being duplicated on twophysical storage devices.
 16. A system comprising: a file system thatreceives and processes file commands to read and write files, said filesystem having a plurality of volumes; a communications layer between anapplication and said file system, said filter that interceptscommunications between said application and said file system; a physicalstorage system comprising a plurality of storage devices and having aphysical storage capacity; a provisioning engine that: allocates storagespace to said volumes, a sum of said storage space allocated to each ofsaid volumes being more storage space than said physical storagecapacity; creates a plurality of space holder files, each of said spaceholder files having an address that is outside any allocated physicaladdress space; identifies a request from said application that consumesphysical storage space within a first volume and determines thatinsufficient storage space is available within said first volume;deletes one of said space holder files from said first volume to free afirst block of space; causes said first block of space to be allocatedonto said physical storage system; and permits said file system to acton said request.
 17. The system of claim 16, each of said volumes beinginitially created with a plurality of space holder files.
 18. The systemof claim 17, at least one of said physical storage devices beingduplicated on a second physical storage device.
 19. The system of claim17, said physical storage devices comprising removable storage devices.20. The system of claim 16, said provisioning system that further:detects that said first volume has unused space greater than a highthreshold; and creates at least one space holder file and deallocatesphysical storage space corresponding to said at least one space holderfile until said first volume has said unused space lower than said highthreshold.